For me, the desired scenario size, as Alan says, is dictated more by the interest in the subject than map size. In fact, I think that I have the following tendencies:
When playing SOLO - Smaller scenarios - not necessarily map size but counter and number of turns seem to dictate what I play - as I have to play in spurts and I don't usually like the games to go on and on and on.
When playing FTF or SKYPE - Any size scenarios - Since these are planned play times, I can set aside the 4-6 hours a session so that I can get bigger ones in. example: Alem Hamza: Right Flank. This was a larger scenario with a large number of turns. Vince and I played it over 4 sessions, each session taking 4-6 hours. It was an epic scenario and I had a lot of fun playing it.
For me, map size is not a problem. I have a ping-pong table in the basement that doubles as my wargaming table, so I can even play a full Cassino scenario if I had to!
